1. Field of the Invention
The present invention relates to a coating apparatus for performing coating, mixing, drying, etc. of particles of a drug, food, agricultural chemicals, etc., and more particularly to a coating apparatus with a rotary drum that is rotated around an axis.
2. Description of the Related Art
In order to provide a film coating, a sugar coating, or the like to a tablet, a soft capsule, a pellet, a granule, and the like (hereinafter, collectively referred to as “particles”) of a drug, food, agricultural chemicals, etc., a coating apparatus with a rotary drum is used.
This type of coating apparatus is also called a pan coating apparatus, and as described, for example, in JP 2003-1083 A, JP 07-328408 A, JP 58-500748 A, JP 2004-97853 A, and JP 2726062 B, the rotary drum includes a body in a polygonal tube shape or a cylindrical shape, and a front wall and a back wall extending from the body in back-and-forth directions, and is placed rotatably around a horizontal axis. Ventilation portions composed of porous portions are provided over the entire circumference of the body or at a plurality of positions of the circumference, and a ventilation jacket covers an outer circumferential side of the respective ventilation portions to form ventilation channels. Each ventilation channel communicates with a supply air duct or an exhaust duct when the ventilation channel reaches a predetermined position along with the rotation of the rotary drum. Thus, treatment gas (e.g., dry air) with the temperature controlled to a predetermined temperature is supplied from the supply air duct into the rotary drum through the ventilation channels and the ventilation portions, and the dry air in the rotary drum is exhausted to the exhaust duct through the ventilation portions and the ventilation channels.
When the rotary drum rotates in a predetermined direction, a particle layer (rolling floor of particle grains) is formed in the rotary drum. Then, a spray solution such as a film agent solution is sprayed onto the particle layer from a spray nozzle placed in the rotary drum, and coating treatment is thus performed.
The spray nozzle for spraying a spray solution is attached to a nozzle support member provided inside a rotary drum in a fixed manner in JP 2003-1083 A and JP 07-328408 A. The nozzle support member is inserted into a hollow driving axis provided on the side of a back end of the rotary drum in JP 2003-1083 A, and is cantilevered at a front end of the rotary drum, and extends toward the side of the back end in JP 07-328408 A. On the other hand, in JP 58-500748 A, the nozzle support member is structured so as to be movable in an axial direction of the rotary drum by means of a slide mechanism, and can be moved through an opening of the front end of the rotary drum.
Furthermore, as described in JP 2004-97853 A and JP 2726062 B, this type of coating apparatus is mostly provided with a discharging mechanism for automatically discharging particle products which have undergone coating treatment. This discharging mechanism is mainly composed of an discharging member provided inside the rotary drum, and rotates the rotary drum in a forward direction (in the same direction as that during treatment of particles) or in a backward direction (in a direction opposite to that during treatment of particles) during discharge, thereby picking up particle products inside the rotary drum with the discharging member, and guiding it to an opening of the front end. Such a discharging member may be attached to the rotary drum only during discharge (JP 2004-97853 A), or may be permanently placed inside the rotary drum (JP 2726062 B). In the former case, the rotation direction of the rotary drum during discharge is either the forward direction or the backward direction, depending upon the setting of the discharging member. In the latter case, the rotation direction of the rotary drum during discharge is always a backward direction.
First, regarding the arrangement of the spray nozzle, in JP 2003-1083 A and JP 07-328408 A, the spray nozzle is attached to the nozzle support member placed inside the rotary drum in a fixed manner, so it is necessary to perform an attachment/detachment operation by inserting hands in the rotary drum at a time of installing or exchanging the spray nozzle, which results in poor operability. On the other hand, in JP 58-50748 A, at a time of installing or exchanging the spray nozzle, the nozzle support member is moved in an axial direction with the slide mechanism, and the nozzle support member can thus be pulled out from the rotary drum. In this case, although the operability is better than that as disclosed in JP 2003-1083 A and JP 07-328408 A, it is necessary to provide the slide mechanism separately, thereby making the configuration of the apparatus be complicated. Furthermore, since the nozzle support member is moved in the axial direction to be pulled out from the rotary drum, a relatively large space is required on a front side of the rotary drum, which may make the layout of the apparatus difficult.
Next, regarding the discharge of particle products, in the discharging mechanism as disclosed in JP 2004-97853 A and JP 2726062 B, the particle products remain in a discharging path, depending upon the shape, property, a discharge amount per unit time, and other conditions of the particle products, with the result that efficient discharge may not be performed.